Many different materials and material configurations have been used to provide strength and structural support to large, portable structures and objects. The portability requires use of a flexible material for it to be folded or rolled for easy transport or storage. Very flexible materials like fabrics can generally have high tensile strength, but the flexible nature that allows folding, rolling and portability indicates that the compressive strength is much less than non-flexible materials.
Some implementations of portable structures employ air-supported elements as a functional structural component. Examples range from U.S. Pat. No. 3,059,657 issued Oct. 23, 1962 to Turner, which discloses a building formed of flexible material that is supported by air pressure within the building to U.S. Pat. No. 3,840,919 issued Oct. 15, 1974 to Middleton, which discloses an inflated tent with hollow ribs having a one-way removable valve. However, despite the ready collapsibility of such approaches, a flexible, conventional material inflated with air can offer only limited structural properties.
In an attempt to overcome some of the deficiencies, other prior art devices have employed means for stiffening the inflatable tubes to provide improved structural support. For example, U.S. Pat. No. 4,514,447 issued Apr. 30, 1985 to Boxmeyer discloses an inflatable structural member that includes resin-impregnated fibers that are cured after the tube is inflated to augment its rigidity. Although successful at providing a more robust structure, such prior art devices cannot be conveniently collapsed for transport, storage or subsequent reuse.
Accordingly, it is an object of the present invention to provide a large inflatable structure that is also easily collapsible while still exhibiting increased rigidity.
It is also an object of the present invention to provide a compact structure that can be inflated for use in a wide variety of portable applications.
A further object of the invention is to provide a sheet material, suitable for incorporation in inflatable or non-inflatable structures, including a unidirectional high (Young's) modulus fiber embedded in a high (Young's) modulus polymer matrix, such that the material exhibits a significantly higher compressive strength along the fiber direction as compared to the perpendicular direction.